Simplify the following expression: $\sqrt{176} - \sqrt{99}$
Explanation: First, try to factor any perfect squares out of the radicals. $= \sqrt{176} - \sqrt{99}$ $= \sqrt{16 \cdot 11} - \sqrt{9 \cdot 11}$ Separate the radicals and simplify. $= \sqrt{16} \cdot \sqrt{11} - \sqrt{9} \cdot \sqrt{11}$ $= 4\sqrt{11} - 3\sqrt{11}$ Finally, simplify by combining the terms. $= ( 4 - 3 )\sqrt{11} = \sqrt{11}$